Conventional internal combustion engines operate according to thermodynamic principles following either a two-stroke cycle or a four-stroke cycle which are commonly classified as a two-stroke engine or a four-stroke engine, respectively. Both types of engines can operate using a range of fuels including gasoline, diesel, alcohol and gaseous fuels. The fuel is typically introduced into the engine using a range of devices including carburetors and fuel injectors, for example. The fuel-air mixture can be ignited by a range of methods including spark ignition and compression ignition. Each engine cycle type has different merits and shortcomings with varying power density, fuel consumption, exhaust emissions, noise, vibration, engine size, weight, cost, etc.
For ordinary driving conditions, a typical vehicle is powered by an engine that is sized for the maximum performance requirement of the vehicle. For example, a passenger vehicle passing another vehicle on a hill may for a brief period utilize the maximum power of the engine. At virtually all other times, from low speed city driving to highway cruising, the power demand is a fraction of the available power. Over-dimensioned engines with large displacements are therefore constructed to meet only occasional power demands.
The situation for large displacement working vehicles is even more dramatic. Freight hauling tractor-trailers, delivery trucks, and other vehicles are designed with engines to accommodate full loads. When traveling empty, the power requirement is substantially diminished. Similarly, marine engines often must shift from high speed or power operation to low speed where the engine operates in idle for long periods of time. Unused displacement or over displacement results in over-sized, large engines with a multiplicity of cylinders, having a weight and complexity resulting in an unnecessary consumption of fuel and excess pollution.
Existing internal combustion engines are usually limited in their operation to two-stroke or four-stroke cycles. The engines have a fixed fuel distribution system, optimized for a limited range of operation. With fixed compression ratios and limited means of optimizing performance for all ranges of power, torque, and engine speed, fuel consumption is typically characterized by a specific fuel consumption curve with one point of minimum fuel consumption.
Although certain improvements to engine design have addressed these problems, for example, the use of a turbocharger for high performance operation, satisfaction of power demand is at the expense of optimized fuel consumption.
Existing internal combustion engines have used switchable cam followers to actuate valves from multiple cam profiles to provide for variations in valve lash between one cam profile to the next. In a conventional system where a rocker arm or a cam follower operate with only a single cam profile, common practice is the use of a hydraulic valve adjuster that is pressurized by lubrication oil and held in a filled position using an internal check valve. These hydraulic valve adjusters have been placed in the block, in the head or in the rocker arm or cam follower itself and are very universal in their application. It is, however, inadequate in valve trains where multiple cam profiles actuate the valves through the use of rocker arms or cam followers that by some means switch from one profile to another.
It would be desirable produce a switching mechanism for switching an engine from two-stroke to four-stroke operation wherein fuel efficiency, emissions efficiency, and power are maximized.